The present invention relates to a method of assembling a color cathode ray tube used for a television receiver, a computer display or the like, and also an apparatus used for assembling the color cathode ray tube.
A typical color cathode ray tube as shown in FIG. 19 comprises a flat or convex color selection electrode 3 opposed to a panel inner surface 1a of a cathode ray tube. The color selection electrode 3 is fixed and held by a color selection electrode frame 4. A panel 1 comprises a plurality of panel pins 2 on the inner surface of its skirt part. One end of each supporting member 5 is engaged with a panel pin 2, while the other end is weld-fixed to the color selection electrode frame 4, and thus the color selection electrode frame 4 is supported by the panel 1 via the supporting members 5.
For setting a spacing (hereinafter referred to also as xe2x80x98Q valuexe2x80x99) between the panel inner surface 1a and the outer surface 3a of the color selection electrode 3, JP-A-9-7504 discloses the following method of assembling a color cathode ray tube.
FIG. 20 shows one of four panel pins 2 provided at the inner surface of the skirt part of the panel 1. Here a virtual plane 2a (indicated by an alternate long and short dash line) is determined by three panel pins 2 as positioning points. Then, distances A1 and A2 between the virtual plane 2a and predetermined points on the panel inner surface 1a are measured.
FIG. 21 shows a pedestal 8 provided with a mask receiver 6 and three dummy pins 7 (only one of the dummy pins is shown). The dummy pin 7 corresponds to the panel pin 2 shown in FIG. 20. On the mask receiver 6, the color selection electrode 3 is placed so that the outer surface 3a is contacted with the upper surface of the mask receiver 6. Furthermore, a color selection electrode frame 4 is prepared by attaching supporting members 5. Each supporting member 5 is supported by three dummy pins 7 so that the color selection electrode frame 4 is held at a position opposing the color selection electrode 3. Here, a virtual panel inner surface 9 is given as a standard curved surface by taking the distance Q value from the outer surface 3a of the color selection electrode 3 into consideration, so that xe2x80x98a1xe2x80x99 and xe2x80x98a2xe2x80x99 denote distances between the virtual flat surface 7a determined by the three dummy pins 7 and predetermined points on the virtual panel inner surface 9. Next, height of each dummy pin 7, i.e., a position of the dummy pin 7 in a Y direction, is adjusted so that the distances xe2x80x98a1xe2x80x99 and xe2x80x98a2xe2x80x99 meet the measured distances A1 and A2. The color selection electrode 3 and the color selection electrode frame 4 are welded to each other under this condition.
Accordingly, the color selection electrode 3 can be located at a predetermined position with respect to the panel 1, without any need for actual positioning of the color selection electrode 3 with respect to the panel 1.
However, the above-described method of assembling a color cathode ray tube cannot satisfy requirements in improving the accuracy of the Q value as a distance between the panel inner surface 1a and the outer surface 3a of the color selection electrode, which is required for providing color cathode ray tubes with high resolution. The reasons follow.
The above-described assembly method requires two devices. One of them shown in FIG. 20 is used for measuring a distance between a virtual flat surface 2a determined by the three panel pins 2 and the panel inner surface 1a. The other device is used for measuring a distance between the virtual flat surface 7a determined by the dummy pins 7 and the virtual panel inner surface 9 in a state that the color selection electrode 3 is placed on the mask receiver 6, and for adjusting the dummy pins 7 to be located at predetermined positions as shown in FIG. 21. The Q value is set on the basis of the measured distances, all of which are obtained respectively by using virtual surfaces. Since the values are not obtained in a direct measurement of the spacing between the panel inner surface 1a and the color selection electrode outer surface 3a, there may be differences between the measured values and a true value, often resulting in variation in the Q value.
This will cause a problem of degraded accuracy of the Q value, i.e., a distance between the panel inner surface 1a and the outer surface 3a of the color selection electrode in a color cathode ray tube as a finished product. Moreover, since the outer surface 3a of the color selection electrode is contacted with the mask receiver 6, the outer surface 3a of the color selection electrode may be dented or scratched. The above-described problems have hindered improvement of the resolution of color cathode ray tubes.
Another problem is the complicated structure, since the two devices for setting the Q values respectively require control circuits for measurement of distances.
It is an object of the invention to provide a method of assembling a color cathode ray tube that can improve the accuracy of the Q value as a distance between a panel inner surface and a color selection electrode outer surface. It is another object of the invention to reduce the occurrence of dents and scratches on the color selection electrode outer surface, and provide for a simple control circuit to be used during a measurement of the Q value.
Methods of and apparatuses for assembling color cathode ray tubes according to the present invention are applied to a color cathode ray tube that has a panel provided with a plurality of panel pins protruding from an inner surface of the panel, a plurality of supporting members provided with engaging holes respectively at first ends, and a color selection electrode frame attached with a color selection electrode, wherein second ends of the supporting members are fixed by welding respectively to the color selection electrode frame, and the engaging holes are engaged respectively with the panel pins.
The assembly method according to the present invention comprises: holding the panel and measuring the position of the inner surface of the panel; holding the color selection electrode frame and measuring the position of the main surface of the color selection electrode attached to the color selection electrode frame; obtaining a measured value corresponding to a spacing between the panel inner surface and the main surface of the color selection electrode on the basis of data of the measured positions; engaging the engaging holes of the supporting members with dummy pins arranged to have a predetermined positional relationship with regard to the positions of the panel pins in the state that the panel is held for the measurement; adjusting the position of the main surface of the color selection electrode with regard to the engaging holes on the basis of the positional relationship and the measured values; and fixing by welding the supporting members to the color selection electrode frame.
This method enables measuring an actual spacing between the panel inner surface and the main surface of the color selection electrode, and improves the accuracy of the Q value.
It is preferable that the dummy pins are arranged at positions separated by a predetermined distance along the axis of the color cathode ray tube from the panel pins in the state in which the panel is held, the panel inner surface is positioned opposing the main surface of the color selection electrode attached to the color selection electrode frame with a certain spacing, and the position of the main surface of the color selection electrode is adjusted with regard to the engaging holes on the basis of the measured values of the spacing between the main surface of the color selection electrode and the panel inner surface.
Thereby, the color selection electrode frame can be welded to the supporting members in a state in which the main surface of the color selection electrode is separated sufficiently from the panel, so that damage to the outer surface of the color selection electrode can be prevented. Moreover, the Q value can be measured with one set of measuring apparatus and thus the control circuit can be simplified.
Alternative processes are as follows. First distances from respective predetermined measurement positions to the panel inner surface are measured in a state in which the panel pins are fitted with panel-pin-fitting holes formed at a shifting mechanism, and then the panel pins are released from the panel-pin-engaging part. Next, the engaging holes of the supporting members are engaged with the dummy pins provided to the shifting mechanism and at the same time the color selection electrode frame is arranged opposing the supporting members. Then, second distances from the respective predetermined measurement positions to the main surface of the color selection electrode attached to the color selection electrode frame are measured. Subsequently, the position of the main surface of the color selection electrode frame is adjusted so that the second distances become equal to respective sums of the respective first distances and a specified value after canceling a distance along the axis of the color cathode ray tube between the position of the panel-pin-fitting holes during the measurement of the first distances and the position of the dummy pins during the measurement of the second distances, and then the supporting members and the color selection electrode frame are welded together.
An assembly apparatus of the present invention comprises: a panel-holding member for holding the panel; dummy pins for engaging with the engaging holes of the supporting members; a frame-shifting mechanism for holding the color selection electrode frame and adjusting the position of the color selection electrode frame; a measuring device for measuring an inner surface position of the panel held by the panel-holding member and also measuring a position of a main surface of the color selection electrode attached to the color selection electrode frame held by the frame-shifting mechanism; and a welding device for fixing by welding together the supporting members having the engaging holes engaged with the dummy pins and the color selection electrode frame held by the frame-shifting mechanism.
It is preferable that the panel-holding member holds the panel and at the same time the frame-shifting mechanism holds the color selection electrode frame so that the main surface of the color selection electrode opposes the inner surface of the panel with a spacing, the dummy pins are positioned with a predetermined distance from the panel pins of the panel held by the panel-holding member along the axis of the color cathode ray tube, and the measuring device measures a spacing between the inner surface of the panel held by the panel-holding member and the main surface of the color selection electrode attached to the color selection electrode frame held by the frame-shifting mechanism.
The assembly apparatus can have the following alternative structure. That is, the assembly apparatus additionally may comprise a shifting mechanism provided with the panel-holding member and the dummy pins, wherein the panel-holding member is composed of panel-pin-fitting holes for fitting with the panel pins so that the panel-holding member selectively holds the panel by an engagement with the panel-pin-fitting holes or the supporting members by an engagement with the dummy pins. The measuring device measures first distances from respective predetermined measurement positions to the panel inner surface in a state in which panel pins are engaged with the panel-pin-fitting holes, and measures second distances from the respective predetermined measurement positions to the main surface of the color selection electrode attached to the color selection electrode frame in a state in which the engaging holes of the supporting members are engaged with the dummy pins. The position of the main surface of the color selection electrode is adjusted with respect to the engaging holes of the supporting members on the basis of the data of the first and second distances.